Method of data transmission in multiple antenna system

ABSTRACT

A method of data transmission includes determining the number of layers, generating mapping symbols by mapping modulation symbols for a first codeword and modulation symbols for a second codeword to each layer, and transmitting the mapping symbols through a plurality of antennas. At least one of the first codeword and the second codeword is mapped to at least 3 layers and the number of layers is larger than 3.

TECHNICAL FIELD

The present invention relates to a multiple antenna system, and moreparticularly, to a method of transmitting a codeword by mapping thecodeword to a layer in the multiple antenna system.

BACKGROUND ART

Wireless communication systems are widely spread all over the world toprovide various types of communication services such as voice or data.Tn general, the wireless communication system is a multiple accesssystem capable of supporting communication with multiple users bysharing available system resources (e.g., bandwidth, transmit (Tx)power, etc.). Examples of the multiple access system include a codedivision multiple access (CDMA) system, a frequency division multipleaccess (FDMA) system, a time division multiple access (TDMA) system, anorthogonal frequency division multiple access (OFDMA) system, a singlecarrier frequency division multiple access (SC-FDMA) system, etc.

The OFDMA is a multiple access scheme for allocating subcarriers havingorthogonality to respective users. The OFDMA can reduce inter-symbolinterference (ISI) and provide a high data rate by supportingcharacteristics robust to frequency selective fading of a channel. Byallocating mutually independent subcarriers to the users, the OFDMAsignificantly decreases a probability that a specific subcarrier is in adeep fading state with respect to all users. Therefore, sincesubcarriers have a mutually independent characteristic between users, Txpower decrease and throughput improvement can be achieved by adaptivelyallocating the subcarriers to a user having a good channel condition.

To overcome performance deterioration caused by channel fading ofwireless communication, many researches have been conducted on spatialdiversity and/or spatial multiplexing using a multiple input multipleoutput (MIMO) system. The MIMO system is implemented so that atransmitter and a receiver have two or more antennas, thereby providingadvantages such as a high data rate, reliability improvement, channelcapacity increase, etc.

Multiple antennas are supported in Institute of electrical andelectronics engineers (IEEE) 802.16 (WiMAX) and 3rd generationpartnership project (3GPP) long term evolution (LTE) for whichstandardization has recently been conducted. As disclosed in 3GPP TS36.211 V8.0.0 (2007-09) “Technical Specification Group Radio AccessNetwork; Evolved Universal Terrestrial Radio Access (E-UTRA); Physicalchannels and modulation (Release 8)”, the 3GPP LTE employs the OFDMA indownlink and employs the SC-FDMA in uplink.

According to the 3GPP TS 36.211 V8.0.0, the 3GPP LTE supports up to 4antenna ports. However, the number of antenna ports is expected to begreater than that in a next generation wireless communication systemrequiring a higher maximum data rate. Therefore, there is a need for amethod of supporting 4 or more antenna ports in a multiple antennasystem.

DISCLOSURE OF INVENTION Technical Problem

The present invention provides a method of transmitting a codeword in amultiple antenna system.

Technical Solution

In an aspect, a method of data transmission in a multiple antenna systemincludes determining the number of layers, generating mapping symbols bymapping modulation symbols for a first codeword and modulation symbolsfor a second codeword to each layer, and transmitting the mappingsymbols through a plurality of antennas. At least one of the firstcodeword and the second codeword is mapped to at least 3 layers and thenumber of layers is larger than 3.

The number of the plurality of antennas may be larger than 3 and thenumber of layers may be smaller than or equal to the number of theplurality of antennas.

The maximum number of layers may be 6 or 8.

The modulation symbols for each codeword may cyclically be mapped toeach layer.

The method may further include retransmitting the first codeword or thesecond codeword. The retransmitting may include determining the newnumber of layers used for retransmission, generating new mapping symbolsby mapping modulation symbols for a codeword to be transmitted to eachlayer, and transmitting the new mapping symbols through the plurality ofantennas. The new number of layers may be smaller than the number oflayers.

The method may further include changing the number of layers into thenew number of layers, generating new mapping symbols by mapping themodulation symbols for the first codeword or the mapping modulationsymbols for the second codeword to each layer, and transmitting the newmapping symbols through the plurality of antennas. The new number oflayers may be smaller than the number of layers.

In another aspect, a transmitter includes a first mapper to generatemodulation symbols for a first codeword, a second mapper to generatemodulation symbols for a second codeword, a layer mapping unit togenerate mapping symbols by mapping modulation symbols for a firstcodeword and modulation symbols for a second codeword to each layer,wherein at least one of the first codeword and the second codeword ismapped to at least 3 layers and the number of layers is larger than 3,and a precoder to process the mapping symbols based on a multiple-inputmultiple-output (MTMO) scheme.

In still another aspect, a communication method in a multiple antennasystem includes establishing basic mapping, determining the use ofextended mapping, and instructing the use of extended mapping. Thenumber of layers used in the basic mapping is greater than the number oflayers used in the extended mapping.

In still another aspect, a method of communication in a multiple antennasystem is provided. The method includes acquiring the number of layers,receiving mapping symbols which are mapped to each layer, demapping themapping symbols to generate modulation symbols for a first codeword ormodulation symbols for a second codeword, wherein at least one of thefirst codeword and the second codeword is mapped to at least 3 layersand the number of layers is larger than 3.

Advantageous Effects

A multiple antenna system having 6 or 8 antenna ports can beimplemented, and an improved data rate and quality of service (QoS) canbe supported.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a wireless communication system.

FIG. 2 is a block diagram showing a transmitter having multiple antennasaccording to an embodiment of the present invention.

FIG. 3 shows layer mapping according to a 1st embodiment of the presentinvention.

FIG. 4 shows extended mapping when layer mapping is performed accordingto a 1st embodiment of the present invention.

FIG. 5 shows layer mapping according to a 2nd embodiment of the presentinvention.

FIG. 6 shows extended mapping when layer mapping is performed accordingto a 2nd embodiment of the present invention.

FIG. 7 shows layer mapping according to a 3rd embodiment of the presentinvention.

FIG. 8 shows extended mapping when layer mapping is performed accordingto a 3rd embodiment of the present invention.

FIG. 9 shows layer mapping according to a 4th embodiment of the presentinvention.

FIG. 10 shows extended mapping when layer mapping is performed accordingto a 4th embodiment of the present invention.

FIG. 11 shows layer mapping according to a 5th embodiment of the presentinvention.

FIG. 12 shows extended mapping when layer mapping is performed accordingto a 5th embodiment of the present invention.

FIG. 13 shows layer mapping according to a 6th embodiment of the presentinvention.

FIG. 14 shows extended mapping when layer mapping is performed accordingto a 6th embodiment of the present invention.

FIG. 15 shows layer mapping according to a 7th embodiment of the presentinvention.

FIG. 16 shows extended mapping when layer mapping is performed accordingto a 7th embodiment of the present invention.

FIG. 17 shows layer mapping according to an 8th embodiment of thepresent invention.

FIG. 18 shows extended mapping when layer mapping is performed accordingto an 8th embodiment of the present invention.

FIG. 19 shows layer mapping according to a 9th embodiment of the presentinvention.

FIG. 20 shows extended mapping when layer mapping is performed accordingto a 9th embodiment of the present invention.

FIG. 21 shows layer mapping according to a 10th embodiment of thepresent invention.

FIG. 22 shows extended mapping when layer mapping is performed accordingto a 10th embodiment of the present invention.

FIG. 23 shows layer mapping according to an 11th embodiment of thepresent invention.

FIG. 24 shows extended mapping when layer mapping is performed accordingto an 11th embodiment of the present invention.

FIG. 25 shows layer mapping according to a 12th embodiment of thepresent invention.

FIG. 26 shows extended mapping in layer mapping according to a 12thembodiment of the present invention.

FIG. 27 shows layer mapping according to a 13th embodiment of thepresent invention.

FIG. 28 shows extended mapping when layer mapping is performed accordingto a 13th embodiment of the present invention.

FIG. 29 shows layer mapping according to a 14th embodiment of thepresent invention.

FIG. 30 shows extended mapping when layer mapping is performed accordingto a 14th embodiment of the present invention.

FIG. 31 shows layer mapping according to a 15th embodiment of thepresent invention.

FIG. 32 shows extended mapping when layer mapping is performed accordingto a 15th embodiment of the present invention.

FIG. 33 shows layer mapping according to a 16th embodiment of thepresent invention.

FIG. 34 shows extended mapping when layer mapping is performed accordingto a 16th embodiment of the present invention.

FIG. 35 is a flow diagram showing triggering from basic mapping toextended mapping by hybrid automatic repeat request (HARQ)retransmission.

FIG. 36 is a flowchart showing triggering from basic mapping to extendedmapping.

FIG. 37 is a flowchart showing a method of data transmission accordingto an embodiment of the present invention.

FIG. 38 is a block diagram showing a transmitter according to anembodiment of the present invention.

FIG. 39 is a flowchart showing a method of communication according to anembodiment of the present invention.

MODE FOR THE INVENTION

The technique, method and apparatus described below can be used invarious wireless access technologies such as code division multipleaccess (CDMA), frequency division multiple access (FDMA), time divisionmultiple access (TDMA), orthogonal frequency division multiple access(OFDMA), single carrier frequency division multiple access (SC-FDMA),etc. The wireless access technologies can be implemented with variouswireless communication standard systems. 3rd generation partnershipproject (3GPP) long term evolution (LTE) is a part of anevolved-universal mobile telecommunications system (E-UMTS). The 3GPPLTE employs the OFDMA in downlink and employs the SC-FDMA in uplink.LTE-advance (LTE-A) is an evolution of the LTE.

For clarity, the following description will focus on the 3GPP LTE/LTE-A.However, technical features of the present invention are not limitedthereto.

The term “or” is intended to mean an inclusive “or” rather than anexclusive “or”. Unless specified otherwise, or clear from the context, aphrase “X employs A or B” is intended to mean any of the naturalinclusive permutations. That is, the phrase “X employs A or B” issatisfied by any of the following instances: X employs A; X employs B;or X employs A and B. In addition, the articles “a” and “an” as used inthis application and the appended claims is generally construed to mean“one or more” unless specified otherwise or clear from the context to bedirected to a singular form.

The technique, method and apparatus described below applies to amultiple antenna system or a multiple input multiple output (MIMO)system using multiple transmit (Tx) antennas and at least one receive(Rx) antenna. The technology described below may apply to various MIMOschemes. The MIMO scheme includes spatial diversity in which the samestream is transmitted to multiple layers and spatial multiplexing inwhich multiple streams are transmitted to multiple layers. When themultiple streams are transmitted to a single user in the spatialmultiplexing, it is called single user-MIMO (SU-MIMO) or spatialdivision multiple access (SDMA). When the multiple streams aretransmitted to multiple users in the spatial multiplexing, it is calledmulti user-MIMO (MU-MTMO). According to whether feedback informationreported from each user is used or not, the spatial diversity and thespatial multiplexing can be classified into an open-loop scheme and aclosed-loop scheme.

FIG. 1 shows a wireless communication system. Referring to FIG. 1, awireless communication system 10 includes at least one base station (BS)11. The BSs 11 provide communication services to specific geographicalregions (generally referred to as cells) 15 a, 15 b, and 15 c. The cellcan be divided into a plurality of regions (referred to as sectors). Auser equipment (UE) 12 may be fixed or mobile, and may be referred to asanother terminology, such as a mobile station (MS), a user terminal(UT), a subscriber station (SS), a wireless device, a personal digitalassistant (PDA), a wireless modem, a handheld device, etc. The BS 11 isgenerally a fixed station that communicates with the UE 12 and may bereferred to as another terminology, such as an evolved node-B (eNB), abase transceiver system (BTS), an access point, etc.

Hereinafter, a downlink denotes a communication link from the BS to theUE, and an uplink denotes a communication link from the UE to the BS. Indownlink, a transmitter may be a part of the BS, and a receiver may be apart of the UE. In uplink, the transmitter may be a part of the UE, andthe receiver may be a part of the BS.

FIG. 2 is a block diagram showing a transmitter having multiple antennasaccording to an embodiment of the present invention.

Referring to FIG. 2, a transmitter 100 includes channel encoders 110-1and 110-2, mappers 120-1 and 120-2, a layer mapping unit 140, a precoder150, and signal generators 160-1, . . . , 160-Nt. Nt denotes the numberof antenna ports. The channel encoders 110-1 and 110-2 encode inputinformation bits according to a predetermined coding scheme to generatecodewords. The first channel encoder 110-1 generates a first codewordCW1, and the second channel encoder 110-2 generates a second codewordCW2.

The mappers 120-1 and 120-2 modulate the respective codewords accordingto a modulation scheme and then map the modulated codewords tomodulation symbols having a demodulation value. There is no restrictionon the modulation scheme. The modulation scheme may be m-phase shiftkeying (m-PSK) or m-quadrature amplitude modulation (m-QAM). Forexample, the m-PSK may be binary-PSK (BPSK), quadrature-PSK (QPSK), or8-PSK. The m-QAM may be 16-QAM, 64-QAM, or 256-QAM. The first mapper120-1 generates modulation symbols for the first codeword CW1. Thesecond mapper 120-2 generates modulation symbols for the second codewordCW2.

Although the transmitter 100 includes the two channel encoders 110-1 and110-2 and the two mappers 120-1 and 120-2 to process the two codewords,the number of channel encoders and the number of mappers included in thetransmitter 100 are not limited thereto. The transmitter 100 may includeat least one channel encoder and at least one mapper to process at leastone codeword.

The layer mapping unit 140 maps modulation symbols of the inputcodewords CW1 and CW2 to each layer according to the number of layers.The layer may be an information path input to the precoder 150. Thelayer corresponds to a rank value. The layer mapping unit 140 maydetermine the number of layers (i.e., rank), and thereafter mapmodulation symbols of each codeword.

The precoder 150 processes a mapping symbol which is mapped to eachlayer by using a MIMO scheme depending on a plurality of antenna ports190-1, . . . , 190-Nt and outputs antenna specific symbols. The signalgenerators 160-1, . . . , 160-Nt convert the antenna specific symbolsinto Tx signals. The Tx signals are transmitted through the respectiveantenna ports 190-1, . . . , 190-Nt. The signal generators 160-1, . . ., 160-Nt may perform orthogonal frequency division multiplexing (OFDM)modulation or may generate a transmit signal by using an SC-FDMAmodulation scheme or other schemes well-known to those skilled in theart.

The transmitter 100 can support hybrid automatic repeat request (HARQ).In a retransmission process for the HARQ, the same layer mapping asinitial transmission may be performed, or layer mapping forretransmission may be performed. Further, the transmitter 100 cansupport rank adaptation in which a rank is changed according to achannel condition.

According to the section 6.3 of 3GPP TS 36.211 V8.0.0 (2007-09), in the3GPP LTE, modulation symbols d^((q))(0), . . . d^((q))(M^((q))_(symb)−1) for a codeword q are mapped to a layer x(i)=[x⁽⁰⁾(i) . . .x^((ν-1))(i)]^(T) (i=0,1, . . . , M^(layer) _(symb)−1). Herein, M^((q))_(symb) denotes the number of modulation symbols for the codeword q, udenotes the number of layers, and M^(layer) _(symb) denotes the numberof modulation symbols for each layer. Table 1 shows codeword-to-layermapping for spatial multiplexing.

Table 1

TABLE 1 Number Number of of code Codeword-to-layer mapping layers wordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽⁰⁾(i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾ 2 2 x⁽⁰⁾(i) = d⁽⁰⁾(i) M_(symb) ^(layer) =M_(symb) ⁽⁰⁾ = M_(symb) ⁽¹⁾ x⁽¹⁾(i) = d⁽¹⁾(i) 3 2 x⁽⁰⁾(i) = d⁽⁰⁾(i)M_(symb) ^(layer) = M_(symb) ⁽⁰⁾ = M_(symb) ⁽¹⁾/2 x⁽¹⁾(i) = d⁽¹⁾(2i)x⁽²⁾(i) = d⁽¹⁾(2i + 1) 4 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) =M_(symb) ⁽⁰⁾/2 = M_(symb) ⁽¹⁾/2 x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) x⁽²⁾(i) =d⁽¹⁾(2i) x⁽³⁾(i) = d⁽¹⁾(2i + 1)

According to Table 1, multi-codeword transmission is supported for up to4 layers, i.e., 4 antenna ports. However, multi-codeword transmissionfor 6 or 8 antenna ports is not provided.

A method described below relates to codeword-to-layer mapping in MIMOtransmission based on at least one codeword for a single user when thenumber of antenna ports is 6 or 8. MIMO transmission for up to twocodewords is designed by considering complexity and feedback overhead ofa system. Backward compatibility with the conventional 3GPP LTE is alsoconsidered.

Parameters to be used hereinafter are defined as follows.

M^((q)) _(symb): the number of modulation symbols for a codeword q

d^((q))(0), . . . , d^((q))(M^((q)) _(symb)−1): modulation symbols forthe codeword q

ν: the number of layers

M^(layer) _(symb): the number of modulation symbols for each layer

x(i)=[x⁽⁰⁾(i) . . . x^((ν-1))(i)]^(T), i=0,1, . . . , M^(layer)_(symb)−1: mapping symbols mapped to layers

In the drawings described below, ‘CWn’ denotes modulation symbols for acodeword n, and ‘S/P’ denotes a serial-to-parallel converter. There isno restriction on MIMO precoding performed in a precoder. Well-knownschemes (e.g., cyclic delay diversity (CDD), space frequency block code(SFCB), space time block code (STBC), and a combination of them) may beused in the MIMO precoding.

FIG. 3 shows layer mapping according to a 1st embodiment of the presentinvention.

Herein, 6 antenna ports are used for layer mapping at ranks 1 to 6. Thiscan be shown by Table 2.

Table 2

TABLE 2 Number Number of of code- Codeword-to-layer mapping, layerswords i = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽⁰⁾(i)M_(symb) ^(layer) = M_(symb) ⁽⁰⁾ 2 2 x⁽⁰⁾(i) = d⁽⁰⁾(i) M_(symb) ^(layer)= M_(symb) ⁽⁰⁾ = M_(symb) ⁽¹⁾ x⁽¹⁾(i) = d⁽¹⁾(i) 3 2 x⁽⁰⁾(i) = d⁽⁰⁾(i)M_(symb) ^(layer) = M_(symb) ⁽⁰⁾ = M_(symb) ⁽¹⁾/2 x⁽¹⁾(i) = d⁽¹⁾(2i)x⁽²⁾(i) = d⁽¹⁾(2i + 1) 4 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) =M_(symb) ⁽⁰⁾/2 = M_(symb) ⁽¹⁾/2 x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) x⁽²⁾(i) =d⁽¹⁾(2i) x⁽³⁾(i) = d⁽¹⁾(2i + 1) 5 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer)= M_(symb) ⁽⁰⁾/2 = M_(symb) ⁽¹⁾/3 x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) x⁽²⁾(i) =d⁽¹⁾(3i) x⁽³⁾(i) = d⁽¹⁾(3i + 1) x⁽⁴⁾(i) = d⁽¹⁾(3i + 2) 6 2 x⁽⁰⁾(i) =d⁽⁰⁾(3i) M_(symb) ^(layer) = M_(symb) ⁽⁰⁾/3 = M_(symb) ⁽¹⁾/3 x⁽¹⁾(i) =d⁽⁰⁾(3i + 1) x⁽²⁾(i) = d⁽⁰⁾(3i + 2) x⁽³⁾(i) = d⁽¹⁾(3i) x⁽⁴⁾(i) =d⁽¹⁾(3i + 1) x⁽⁵⁾(i) = d⁽¹⁾(3i + 2)

At the rank 3, a first codeword CW1 may be mapped to a first layer, anda second codeword CW2 may be arranged in a second layer and a thirdlayer. Thus, a gain can be obtained when a receiver performs successiveinterference cancellation (SIC).

At the rank 4 or higher, inter-layer interference may be increased inproportion to the number of layers to be mapped for each codeword.According to the aforementioned layer mapping, codeword decodingperformance can be optimized by equalizing codeword symbols to be mappedto each layer as much as possible. When the receiver performs the SIC,interference cancellation between layers mapped to the second codewordCW2 may be supported according to a channel decoding result of the firstcodeword CW1 or according to a soft value of a symbol level.

FIG. 4 shows extended mapping when layer mapping is performed accordingto the 1st embodiment of the present invention. This can be shown byTable 3.

Table 3

TABLE 3 Number of Number code- Codeword-to-layer mapping, of layerswords i = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽¹⁾(i)M_(symb) ^(layer) = M_(symb) ⁽¹⁾ 2 1 x⁽⁰⁾(i) = d^((n))(2i) M_(symb)^(layer) = M_(symb) ^((n))/2, n = 1 or 2 x⁽¹⁾(i) = d^((n))(2i + 1) 3 1x⁽⁰⁾(i) = d^((n))(3i) M_(symb) ^(layer) = M_(symb) ^((n))/3, n = 1 or 2x⁽¹⁾(i) = d^((n))(3i + 1) x⁽²⁾(i) = d^((n))(3i + 2)

The extended mapping may be used as layer mapping for HARQ resources.When transmission of a first codeword is successful and transmission ofa second codeword fails in initial transmission, the extended mapping islayer mapping for the failed codeword (i.e., the second codeword).Alternatively, the extended mapping may be used as layer mapping forsupporting rank overriding.

FIG. 5 shows layer mapping according to a 2nd embodiment of the presentinvention. Herein, 6 antenna ports are used for layer mapping at ranks 1to 6. In single codeword transmission at the rank 2 or lower,transmission performance can be improved by increasing a channel codinggain of a codeword. This can be shown by Table 4.

Table 4

TABLE 4 Number Number of of code- Codeword-to-layer mapping, layerswords i = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽⁰⁾(i)M_(symb) ^(layer) = M_(symb) ⁽⁰⁾ 2 1 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/2 x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) 3 2 x⁽⁰⁾(i) = d⁽⁰⁾(i)M_(symb) ^(layer) = M_(symb) ⁽⁰⁾ = M_(symb) ⁽¹⁾/2 x⁽¹⁾(i) = d⁽¹⁾(2i)x⁽²⁾(i) = d⁽¹⁾(2i + 1) 4 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) =M_(symb) ⁽⁰⁾/2 = M_(symb) ⁽¹⁾/2 x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) x⁽²⁾(i) =d⁽¹⁾(2i) x⁽³⁾(i) = d⁽¹⁾(2i + 1) 5 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer)= M_(symb) ⁽⁰⁾/2 = M_(symb) ⁽¹⁾/3 x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) x⁽²⁾(i) =d⁽¹⁾(3i) x⁽³⁾(i) = d⁽¹⁾(3i + 1) x⁽⁴⁾(i) = d⁽¹⁾(3i + 2) 6 2 x⁽⁰⁾(i) =d⁽⁰⁾(3i) M_(symb) ^(layer) = M_(symb) ⁽⁰⁾/3 = M_(symb) ⁽¹⁾/3 x⁽¹⁾(i) =d⁽⁰⁾(3i + 1) x⁽²⁾(i) = d⁽⁰⁾(3i + 2) x⁽³⁾(i) = d⁽¹⁾(3i) x⁽⁴⁾(i) =d⁽¹⁾(3i + 1) x⁽⁵⁾(i) = d⁽¹⁾(3i + 2)

FIG. 6 shows extended mapping when layer mapping is performed accordingto the 2nd embodiment of the present invention. The extended mapping isused to support HARQ retransmission or rank overriding, and this can beshown by Table 5.

Table 5

TABLE 5 Number of Number of Codeword-to-layer mapping, layers codewordsi = 0, 1, ..., M_(symb) ^(layer) − 1 2 1 x⁽⁰⁾(i) = d⁽¹⁾(2i) M_(symb)^(layer) = M_(symb) ⁽¹⁾/2 x⁽¹⁾(i) = d⁽¹⁾(2i + 1) 3 1 x⁽⁰⁾(i) =d^((n))(3i) M_(symb) ^(layer) = M_(symb) ^((n))/3, n = 1 or 2 x⁽¹⁾(i) =d^((n))(3i + 1) x⁽²⁾(i) = d^((n))(3i + 2)

FIG. 7 shows layer mapping according to a 3rd embodiment of the presentinvention. Herein, 6 antenna ports are used for layer mapping at ranks 1to 6. In single codeword transmission at the rank 3 or lower,transmission performance can be improved by increasing a channel codinggain of a codeword. This can be shown by Table 6.

Table 6

TABLE 6 Number Number of of code- Codeword-to-layer mapping, layerswords i = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽⁰⁾(i)M_(symb) ^(layer) = M_(symb) ⁽⁰⁾ 2 1 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/2 x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) 3 1 x⁽⁰⁾(i) = d⁽⁰⁾(3i)M_(symb) ^(layer) = M_(symb) ⁽⁰⁾/3 x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) x⁽²⁾(i) =d⁽⁰⁾(3i + 2) 4 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) = M_(symb) ⁽⁰⁾/2 =M_(symb) ⁽¹⁾/2 x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) x⁽²⁾(i) = d⁽¹⁾(2i) x⁽³⁾(i) =d⁽¹⁾(2i + 1) 5 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) = M_(symb) ⁽⁰⁾/2 =M_(symb) ⁽¹⁾/3 x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) x⁽²⁾(i) = d⁽¹⁾(3i) x⁽³⁾(i) =d⁽¹⁾(3i + 1) x⁽⁴⁾(i) = d⁽¹⁾(3i + 2) 6 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/3 = M_(symb) ⁽¹⁾/3 x⁽¹⁾(i) = d⁽⁰⁾(3i + 1)x⁽²⁾(i) = d⁽⁰⁾(3i + 2) x⁽³⁾(i) = d⁽¹⁾(3i) x⁽⁴⁾(i) = d⁽¹⁾(3i + 1) x⁽⁵⁾(i)= d⁽¹⁾(3i + 2)

FIG. 8 shows extended mapping when layer mapping is performed accordingto the 3rd embodiment of the present invention. The extended mapping isused to support HARQ retransmission or rank overriding, and this can beshown by Table 7.

Table 7

TABLE 7 Number Number Codeword-to-layer mapping, of layers of codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 2 1 x⁽⁰⁾(i) = d⁽¹⁾(2i) M_(symb)^(layer) = M_(symb) ⁽¹⁾/2 x⁽¹⁾(i) = d⁽¹⁾(2i + 1) 3 1 x⁽⁰⁾(i) = d⁽¹⁾(3i)M_(symb) ^(layer) = M_(symb) ⁽¹⁾/3 x⁽¹⁾(i) = d⁽¹⁾(3i + 1) x⁽²⁾(i) =d⁽¹⁾(3i + 2)

FIG. 9 shows layer mapping according to a 4th embodiment of the presentinvention. Herein, 6 antenna ports are used for layer mapping at ranks 1to 6. In single codeword transmission at the rank 3 or lower, a changein an aspect of mapping each codeword to layers at different ranks isminimized. In transmission using active rank adaptation, disparitybetween a modulation and coding scheme (MCS) used in transmission and achannel quality indicator (CQT) reported by the UE depending on the rankchange can be minimized. This can be shown by Table 8.

Table 8

TABLE 8 Number Number of of code- Codeword-to-layer mapping, layerswords i = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽⁰⁾(i)M_(symb) ^(layer) = M_(symb) ⁽⁰⁾ 2 1 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/2 x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) 3 1 x⁽⁰⁾(i) = d⁽⁰⁾(3i)M_(symb) ^(layer) = M_(symb) ⁽⁰⁾/3 x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) x⁽²⁾(i) =d⁽⁰⁾(3i + 2) 4 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb) ^(layer) = M_(symb) ⁽⁰⁾/3 =M_(symb) ⁽¹⁾ x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) x⁽²⁾(i) = d⁽⁰⁾(3i + 2) x⁽³⁾(i) =d⁽¹⁾(i) 5 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) = M_(symb) ⁽⁰⁾/2 =M_(symb) ⁽¹⁾/3 x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) x⁽²⁾(i) = d⁽¹⁾(3i) x⁽³⁾(i) =d⁽¹⁾(3i + 1) x⁽⁴⁾(i) = d⁽¹⁾(3i + 2) 6 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/3 = M_(symb) ⁽¹⁾/3 x⁽¹⁾(i) = d⁽⁰⁾(3i + 1)x⁽²⁾(i) = d⁽⁰⁾(3i + 2) x⁽³⁾(i) = d⁽¹⁾(3i) x⁽⁴⁾(i) = d⁽¹⁾(3i + 1) x⁽⁵⁾(i)= d⁽¹⁾(3i + 2)

FIG. 10 shows extended mapping when layer mapping is performed accordingto the 4th embodiment of the present invention. The extended mapping isused to support HARQ retransmission or rank overriding, and this can beshown by Table 9.

Table 9

TABLE 9 Number of Number Codeword-to-layer mapping, layers of codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽¹⁾(i) M_(symb)^(layer) = M_(symb) ⁽¹⁾ 2 1 x⁽⁰⁾(i) = d⁽¹⁾(2i) M_(symb) ^(layer) =M_(symb) ⁽¹⁾/2 x⁽¹⁾(i) = d⁽¹⁾(2i + 1) 3 1 x⁽⁰⁾(i) = d⁽¹⁾(3i) M_(symb)^(layer) = M_(symb) ⁽¹⁾/3 x⁽¹⁾(i) = d⁽¹⁾(3i + 1) x⁽²⁾(i) = d⁽¹⁾(3i + 2)

FIG. 11 shows layer mapping according to a 5th embodiment of the presentinvention. Herein, 6 antenna ports are used for layer mapping at ranks 1to 6. When the receiver performs the SIC, layer mapping on each codewordis naturally increased according to a codeword index along with theincrease of the ranks while codeword symbols mapped to each layer areequalized as mush as possible, thereby optimizing codeword decodingperformance. This can be shown by Table 10.

Table 10

TABLE 10 Number Number of of code- Codeword-to-layer mapping, layerswords i = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽⁰⁾(i)M_(symb) ^(layer) = M_(symb) ⁽⁰⁾ 2 2 x⁽⁰⁾(i) = d⁽⁰⁾(i) M_(symb) ^(layer)= M_(symb) ⁽⁰⁾ = M_(symb) ⁽¹⁾ x⁽¹⁾(i) = d⁽¹⁾(i) 3 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i)M_(symb) ^(layer) = M_(symb) ⁽⁰⁾/2 = M_(symb) ⁽¹⁾ x⁽¹⁾(i) = d⁽⁰⁾(2i + 1)x⁽²⁾(i) = d⁽¹⁾(i) 4 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) = M_(symb)⁽⁰⁾/2 = M_(symb) ⁽¹⁾/2 x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) x⁽²⁾(i) = d⁽¹⁾(2i) x⁽³⁾(i)= d⁽¹⁾(2i + 1) 5 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb) ^(layer) = M_(symb) ⁽⁰⁾/3= M_(symb) ⁽¹⁾/2 x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) x⁽²⁾(i) = d⁽⁰⁾(3i + 2) x⁽³⁾(i) =d⁽¹⁾(2i) x⁽⁴⁾(i) = d⁽¹⁾(2i + 1) 6 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb) ^(layer)= M_(symb) ⁽⁰⁾/3 = M_(symb) ⁽¹⁾/3 x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) x⁽²⁾(i) =d⁽⁰⁾(3i + 2) x⁽³⁾(i) = d⁽¹⁾(3i) x⁽⁴⁾(i) = d⁽¹⁾(3i + 1) x⁽⁵⁾(i) =d⁽¹⁾(3i + 2)

FIG. 12 shows extended mapping when layer mapping is performed accordingto the 5th embodiment of the present invention. The extended mapping isused to support HARQ retransmission or rank overriding, and this can beshown by Table 11.

Table 11

TABLE 11 Number of Number of Codeword-to-layer mapping, layers codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽¹⁾(i) M_(symb)^(layer) = M_(symb) ⁽¹⁾ 2 1 x⁽⁰⁾(i) = d^((n))(2i) M_(symb) ^(layer) =M_(symb) ^((n))/2, n = 1 or 2 x⁽¹⁾(i) = d^((n))(2i + 1) 3 1 x⁽⁰⁾(i) =d^((n))(3i) M_(symb) ^(layer) = M_(symb) ^((n))/3, n = 1 or 2 x⁽¹⁾(i) =d^((n))(3i + 1) x⁽²⁾(i) = d^((n))(3i + 2)

FIG. 13 shows layer mapping according to a 6th embodiment of the presentinvention. Herein, 6 antenna ports are used for layer mapping at ranks 1to 6. Only a single codeword is transmitted at the rank 2 or lower bybasically using the layer mapping according to the 5th embodiment. Thus,when an SCI gain of the receiver is small, transmission performance canbe improved by increasing a channel coding gain of the single codeword.This can be shown by Table 12.

Table 12

TABLE 12 Number Number of of code- Codeword-to-layer mapping, layerswords i = 0, 1, ..., M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽⁰⁾(i)M_(symb) ^(layer) = M_(symb) ⁽⁰⁾ 2 1 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/2 x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) 3 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i)M_(symb) ^(layer) = M_(symb) ⁽⁰⁾/2 = M_(symb) ⁽¹⁾ x⁽¹⁾(i) = d⁽⁰⁾(2i + 1)x⁽²⁾(i) = d⁽¹⁾(i) 4 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) = M_(symb)⁽⁰⁾/2 = M_(symb) ⁽¹⁾/2 x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) x⁽²⁾(i) = d⁽¹⁾(2i) x⁽³⁾(i)= d⁽¹⁾(2i + 1) 5 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb) ^(layer) = M_(symb) ⁽⁰⁾/3= M_(symb) ⁽¹⁾/2 x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) x⁽²⁾(i) = d⁽⁰⁾(3i + 2) x⁽³⁾(i) =d⁽¹⁾(2i) x⁽⁴⁾(i) = d⁽¹⁾(2i + 1) 6 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb) ^(layer)= M_(symb) ⁽⁰⁾/3 = M_(symb) ⁽¹⁾/3 x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) x⁽²⁾(i) =d⁽⁰⁾(3i + 2) x⁽³⁾(i) = d⁽¹⁾(3i) x⁽⁴⁾(i) = d⁽¹⁾(3i + 1) x⁽⁵⁾(i) =d⁽¹⁾(3i + 2)

FIG. 14 shows extended mapping when layer mapping is performed accordingto the 6th embodiment of the present invention. The extended mapping isused to support HARQ retransmission or rank overriding, and this can beshown by Table 13.

Table 13

TABLE 13 Number Number Codeword-to-layer mapping, of layers of codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽¹⁾(i) M_(symb)^(layer) = M_(symb) ⁽¹⁾ 2 1 x⁽⁰⁾(i) = d⁽¹⁾(2i) M_(symb) ^(layer) =M_(symb) ⁽¹⁾/2 x⁽¹⁾(i) = d⁽¹⁾(2i + 1) 3 1 x⁽⁰⁾(i) = d^((n))(3i) M_(symb)^(layer) = x⁽¹⁾(i) = d^((n))(3i + 1) M_(symb) ^((n))/3, n = 1 or 2x⁽²⁾(i) = d^((n))(3i + 2)

FIG. 15 shows layer mapping according to a 7th embodiment of the presentinvention. Herein, 6 antenna ports are used for layer mapping at ranks 1to 6. Only a single codeword is transmitted at the rank 2 or lower bybasically using the layer mapping according to the 5th embodiment. Thus,when the SCI gain of the receiver is small, transmission performance canbe improved by increasing a channel coding gain of the single codeword.This can be shown by Table 14.

Table 14

TABLE 14 Number Number Codeword-to-layer mapping, of layers of codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽⁰⁾(i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾ 2 1 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) =M_(symb) ⁽⁰⁾/2 x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) 3 1 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/3 x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) x⁽²⁾(i) = d⁽⁰⁾(3i + 2)4 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) = x⁽¹⁾(i) = d⁽⁰⁾(2i + 1)M_(symb) ⁽⁰⁾/2 = M_(symb) ⁽¹⁾/2 x⁽²⁾(i) = d⁽¹⁾(2i) x⁽³⁾(i) =d⁽¹⁾(2i + 1) 5 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb) ^(layer) = x⁽¹⁾(i) =d⁽⁰⁾(3i + 1) M_(symb) ⁽⁰⁾/3 = M_(symb) ⁽¹⁾/2 x⁽²⁾(i) = d⁽⁰⁾(3i + 2)x⁽³⁾(i) = d⁽¹⁾(2i) x⁽⁴⁾(i) = d⁽¹⁾(2i + 1) 6 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i)M_(symb) ^(layer) = x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) M_(symb) ⁽⁰⁾/3 = M_(symb)⁽¹⁾/3 x⁽²⁾(i) = d⁽⁰⁾(3i + 2) x⁽³⁾(i) = d⁽¹⁾(3i) x⁽⁴⁾(i) = d⁽¹⁾(3i + 1)x⁽⁵⁾(i) = d⁽¹⁾(3i + 2)

FIG. 16 shows extended mapping when layer mapping is performed accordingto the 7th embodiment of the present invention. The extended mapping isused to support HARQ retransmission or rank overriding, and this can beshown by Table 15.

Table 15

TABLE 15 Number Number Codeword-to-layer mapping, of layers of codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 2 1 x⁽⁰⁾(i) = d⁽¹⁾(2i) M_(symb)^(layer) = M_(symb) ⁽¹⁾/2 x⁽¹⁾(i) = d⁽¹⁾(2i + 1) 3 1 x⁽⁰⁾(i) = d⁽¹⁾(3i)M_(symb) ^(layer) = M_(symb) ⁽¹⁾/3 x⁽¹⁾(i) = d⁽¹⁾(3i + 1) x⁽²⁾(i) =d⁽¹⁾(3i + 2)

FIG. 17 shows layer mapping according to an 8th embodiment of thepresent invention. Herein, 6 antenna ports are used for layer mapping atranks 1 to 6.

Only a single codeword is transmitted at the rank 3 or lower bybasically using the layer mapping according to the 5th embodiment. Achange in an aspect of mapping each codeword to layers at differentranks is minimized. In transmission using active rank adaptation,disparity between the MCS used in transmission and the CQI reported bythe UE depending on the rank change can be minimized. This can be shownby Table 16.

Table 16

TABLE 16 Number Number Codeword-to-layer mapping, of layers of codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽⁰⁾(i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾ 2 1 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) =M_(symb) ⁽⁰⁾/2 x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) 3 1 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/3 x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) x⁽²⁾(i) = d⁽⁰⁾(3i + 2)4 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb) ^(layer) = x⁽¹⁾(i) = d⁽⁰⁾(3i + 1)M_(symb) ⁽⁰⁾/3 = M_(symb) ⁽¹⁾ x⁽²⁾(i) = d⁽⁰⁾(3i + 2) x⁽³⁾(i) = d⁽¹⁾(i) 52 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb) ^(layer) = x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) M_(symb)⁽⁰⁾/3 = M_(symb) ⁽¹⁾/2 x⁽²⁾(i) = d⁽⁰⁾(3i + 2) x⁽³⁾(i) = d⁽¹⁾(2i) x⁽⁴⁾(i)= d⁽¹⁾(2i + 1) 6 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb) ^(layer) = x⁽¹⁾(i) =d⁽⁰⁾(3i + 1) M_(symb) ⁽⁰⁾/3 = M_(symb) ⁽¹⁾/3 x⁽²⁾(i) = d⁽⁰⁾(3i + 2)x⁽³⁾(i) = d⁽¹⁾(3i) x⁽⁴⁾(i) = d⁽¹⁾(3i + 1) x⁽⁵⁾(i) = d⁽¹⁾(3i + 2)

FIG. 18 shows extended mapping when layer mapping is performed accordingto the 8th embodiment of the present invention. The extended mapping isused to support HARQ retransmission or rank overriding, and this can beshown by Table 17.

Table 17

TABLE 17 Number Number Codeword-to-layer mapping, of layers of codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽¹⁾(i) M_(symb)^(layer) = M_(symb) ⁽¹⁾ 2 1 x⁽⁰⁾(i) = d⁽¹⁾(2i) M_(symb) ^(layer) =M_(symb) ⁽¹⁾/2 x⁽¹⁾(i) = d⁽¹⁾(2i + 1) 3 1 x⁽⁰⁾(i) = d⁽¹⁾(3i) M_(symb)^(layer) = M_(symb) ⁽¹⁾/3 x⁽¹⁾(i) = d⁽¹⁾(3i + 1) x⁽²⁾(i) = d⁽¹⁾(3i + 2)

In layer mapping to be described now, 8 antenna ports are used at ranks1 to 8.

FIG. 19 shows layer mapping according to a 9th embodiment of the presentinvention. At the rank 4 or higher, inter-layer interference mayincrease in proportion to the number of layers to be mapped for eachcodeword. Thus, codeword decoding performance can be optimized byequalizing codeword symbols to be mapped to each layer as much aspossible. This is for supporting backward compatibility with the 3GPPLTE. A mapping method for each rank can be shown by Tables 18 and 19.

Table 18

TABLE 18 Number Number Codeword-to-layer mapping, of layers of codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽⁰⁾(i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾ 2 2 x⁽⁰⁾(i) = d⁽⁰⁾(i) M_(symb) ^(layer) =x⁽¹⁾(i) = d⁽¹⁾(i) M_(symb) ⁽⁰⁾ = M_(symb) ⁽¹⁾ 3 2 x⁽⁰⁾(i) = d⁽⁰⁾(i)M_(symb) ^(layer) = x⁽¹⁾(i) = d⁽¹⁾(2i) M_(symb) ⁽⁰⁾ = M_(symb) ⁽¹⁾/2x⁽²⁾(i) = d⁽¹⁾(2i + 1) 4 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) =x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) M_(symb) ⁽⁰⁾/2 = M_(symb) ⁽¹⁾/2 x⁽²⁾(i) =d⁽¹⁾(2i) x⁽³⁾(i) = d⁽¹⁾(2i + 1) 5 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer)= x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) M_(symb) ⁽⁰⁾/2 = M_(symb) ⁽¹⁾/3 x⁽²⁾(i) =d⁽¹⁾(3i) x⁽³⁾(i) = d⁽¹⁾(3i + 1) x⁽⁴⁾(i) = d⁽¹⁾(3i + 2) 6 2 x⁽⁰⁾(i) =d⁽⁰⁾(3i) M_(symb) ^(layer) = x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) M_(symb) ⁽⁰⁾/3 =M_(symb) ⁽¹⁾/3 x⁽²⁾(i) = d⁽⁰⁾(3i + 2) x⁽³⁾(i) = d⁽¹⁾(3i) x⁽⁴⁾(i) =d⁽¹⁾(3i + 1) x⁽⁵⁾(i) = d⁽¹⁾(3i + 2)

Table 19

TABLE 19 Number of Number Codeword-to-layer mapping, layers of codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 7 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb)^(layer) = x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) M_(symb) ⁽⁰⁾/3 = M_(symb) ⁽¹⁾/4x⁽²⁾(i) = d⁽⁰⁾(3i + 2) x⁽³⁾(i) = d⁽¹⁾(4i) x⁽⁴⁾(i) = d⁽¹⁾(4i + 1) x⁽⁵⁾(i)= d⁽¹⁾(4i + 2) x⁽⁶⁾(i) = d⁽¹⁾(4i + 3) 8 2 x⁽⁰⁾(i) = d⁽⁰⁾(4i) M_(symb)^(layer) = x⁽¹⁾(i) = d⁽⁰⁾(4i + 1) M_(symb) ⁽⁰⁾/4 = M_(symb) ⁽¹⁾/4x⁽²⁾(i) = d⁽⁰⁾(4i + 2) x⁽³⁾(i) = d⁽⁰⁾(4i + 3) x⁽⁴⁾(i) = d⁽¹⁾(4i) x⁽⁵⁾(i)= d⁽¹⁾(4i + 1) x⁽⁶⁾(i) = d⁽¹⁾(4i + 2) x⁽⁷⁾(i) = d⁽¹⁾(4i + 3)

FIG. 20 shows extended mapping when layer mapping is performed accordingto the 9th embodiment of the present invention. The extended mapping isused to support HARQ retransmission or rank overriding, and this can beshown by Table 20.

Table 20

TABLE 20 Number of Number Codeword-to-layer mapping, layers of codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽¹⁾(i) M_(symb)^(layer) = M_(symb) ⁽¹⁾ 2 1 x⁽⁰⁾(i) = d^((n))(2i) M_(symb) ^(layer) =x⁽¹⁾(i) = d^((n))(2i + 1) M_(symb) ^((n))/2, n = 1 or 2 3 1 x⁽⁰⁾(i) =d^((n))(3i) M_(symb) ^(layer) = x⁽¹⁾(i) = d^((n))(3i + 1) M_(symb)^((n))/3, n = 1 or 2 x⁽²⁾(i) = d^((n))(3i + 2) 4 1 x⁽⁰⁾(i) = d^((n))(4i)M_(symb) ^(layer) = x⁽¹⁾(i) = d^((n))(4i + 1) M_(symb) ^((n))/4, n = 1or 2 x⁽²⁾(i) = d^((n))(4i + 2) x⁽³⁾(i) = d^((n))(4i + 3)

FIG. 21 shows layer mapping according to a 10th embodiment of thepresent invention. In single codeword transmission at a rank 2 or lower,transmission performance can be improved by increasing a channel codinggain of a codeword. This can be shown by Tables 21 and 22.

Table 21

TABLE 21 Number of Number Codeword-to-layer mapping, layers of codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽⁰⁾(i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾ 2 1 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) =M_(symb) ⁽⁰⁾/2 x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) 3 2 x⁽⁰⁾(i) = d⁽⁰⁾(i) M_(symb)^(layer) = x⁽¹⁾(i) = d⁽¹⁾(2i) M_(symb) ⁽⁰⁾ = M_(symb) ⁽¹⁾/2 x⁽²⁾(i) =d⁽¹⁾(2i + 1) 4 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) = x⁽¹⁾(i) =d⁽⁰⁾(2i + 1) M_(symb) ⁽⁰⁾/2 = M_(symb) ⁽¹⁾/2 x⁽²⁾(i) = d⁽¹⁾(2i) x⁽³⁾(i)= d⁽¹⁾(2i + 1) 5 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) = x⁽¹⁾(i) =d⁽⁰⁾(2i + 1) M_(symb) ⁽⁰⁾/2 = M_(symb) ⁽¹⁾/3 x⁽²⁾(i) = d⁽¹⁾(3i) x⁽³⁾(i)= d⁽¹⁾(3i + 1) x⁽⁴⁾(i) = d⁽¹⁾(3i + 2) 6 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb)^(layer) = x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) M_(symb) ⁽⁰⁾/3 = M_(symb) ⁽¹⁾/3x⁽²⁾(i) = d⁽⁰⁾(3i + 2) x⁽³⁾(i) = d⁽¹⁾(3i) x⁽⁴⁾(i) = d⁽¹⁾(3i + 1) x⁽⁵⁾(i)= d⁽¹⁾(3i + 2)

Table 22

TABLE 22 Number of Number Codeword-to-layer mapping, layers of codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 7 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb)^(layer) = x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) M_(symb) ⁽⁰⁾/3 = M_(symb) ⁽¹⁾/4x⁽²⁾(i) = d⁽⁰⁾(3i + 2) x⁽³⁾(i) = d⁽¹⁾(4i) x⁽⁴⁾(i) = d⁽¹⁾(4i + 1) x⁽⁵⁾(i)= d⁽¹⁾(4i + 2) x⁽⁶⁾(i) = d⁽¹⁾(4i + 3) 8 2 x⁽⁰⁾(i) = d⁽⁰⁾(4i) M_(symb)^(layer) = x⁽¹⁾(i) = d⁽⁰⁾(4i + 1) M_(symb) ⁽⁰⁾/4 = M_(symb) ⁽¹⁾/4x⁽²⁾(i) = d⁽⁰⁾(4i + 2) x⁽³⁾(i) = d⁽⁰⁾(4i + 3) x⁽⁴⁾(i) = d⁽¹⁾(4i) x⁽⁵⁾(i)= d⁽¹⁾(4i + 1) x⁽⁶⁾(i) = d⁽¹⁾(4i + 2) x⁽⁷⁾(i) = d⁽¹⁾(4i + 3)

FIG. 22 shows extended mapping when layer mapping is performed accordingto the 10th embodiment of the present invention. The extended mapping isused to support HARQ retransmission or rank overriding, and this can beshown by Table 23.

Table 23

TABLE 23 Number of Number Codeword-to-layer mapping, layers of codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 2 1 x⁽⁰⁾(i) = d⁽¹⁾(2i) M_(symb)^(layer) = M_(symb) ⁽¹⁾/2 x⁽¹⁾(i) = d⁽¹⁾(2i + 1) 3 1 x⁽⁰⁾(i) =d^((n))(3i) M_(symb) ^(layer) = x⁽¹⁾(i) = d^((n))(3i + 1) M_(symb)^((n))/3, n = 1 or 2 x⁽²⁾(i) = d^((n))(3i + 2) 4 1 x⁽⁰⁾(i) = d^((n))(4i)M_(symb) ^(layer) = x⁽¹⁾(i) = d^((n))(4i + 1) M_(symb) ^((n))/4, n = 1or 2 x⁽²⁾(i) = d^((n))(4i + 2) x⁽³⁾(i) = d^((n))(4i + 3)

FIG. 23 shows layer mapping according to an 11th embodiment of thepresent invention. In single codeword transmission at a rank 3 or lower,transmission performance can be improved by increasing a channel codinggain of a codeword. This can be shown by Tables 24 and 25.

Table 24

TABLE 24 Number of Number Codeword-to-layer mapping, layers of codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽⁰⁾(i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾ 2 1 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) =M_(symb) ⁽⁰⁾/2 x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) 3 1 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/3 x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) x⁽²⁾(i) = d⁽⁰⁾(3i + 2)4 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) = x⁽¹⁾(i) = d⁽⁰⁾(2i + 1)M_(symb) ⁽⁰⁾/2 = M_(symb) ⁽¹⁾/2 x⁽²⁾(i) = d⁽¹⁾(2i) x⁽³⁾(i) =d⁽¹⁾(2i + 1) 5 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) = x⁽¹⁾(i) =d⁽⁰⁾(2i + 1) M_(symb) ⁽⁰⁾/2 = M_(symb) ⁽¹⁾/3 x⁽²⁾(i) = d⁽¹⁾(3i) x⁽³⁾(i)= d⁽¹⁾(3i + 1) x⁽⁴⁾(i) = d⁽¹⁾(3i + 2) 6 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb)^(layer) = x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) M_(symb) ⁽⁰⁾/3 = M_(symb) ⁽¹⁾/3x⁽²⁾(i) = d⁽⁰⁾(3i + 2) x⁽³⁾(i) = d⁽¹⁾(3i) x⁽⁴⁾(i) = d⁽¹⁾(3i + 1) x⁽⁵⁾(i)= d⁽¹⁾(3i + 2)

Table 25

TABLE 25 Number of Number Codeword-to-layer mapping, layers of codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 7 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb)^(layer) = x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) M_(symb) ⁽⁰⁾/3 = M_(symb) ⁽¹⁾/4x⁽²⁾(i) = d⁽⁰⁾(3i + 2) x⁽³⁾(i) = d⁽¹⁾(4i) x⁽⁴⁾(i) = d⁽¹⁾(4i + 1) x⁽⁵⁾(i)= d⁽¹⁾(4i + 2) x⁽⁶⁾(i) = d⁽¹⁾(4i + 3) 8 2 x⁽⁰⁾(i) = d⁽⁰⁾(4i) M_(symb)^(layer) = x⁽¹⁾(i) = d⁽⁰⁾(4i + 1) M_(symb) ⁽⁰⁾/4 = M_(symb) ⁽¹⁾/4x⁽²⁾(i) = d⁽⁰⁾(4i + 2) x⁽³⁾(i) = d⁽⁰⁾(4i + 3) x⁽⁴⁾(i) = d⁽¹⁾(4i) x⁽⁵⁾(i)= d⁽¹⁾(4i + 1) x⁽⁶⁾(i) = d⁽¹⁾(4i + 2) x⁽⁷⁾(i) = d⁽¹⁾(4i + 3)

FIG. 24 shows extended mapping when layer mapping is performed accordingto the 11th embodiment of the present invention. The extended mapping isused to support HARQ retransmission or rank overriding, and this can beshown by Table 26.

Table 26

TABLE 26 Number Number Codeword-to-layer mapping, of layers of codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 2 1 x⁽⁰⁾(i) = d⁽¹⁾(2i) M_(symb)^(layer) = M_(symb) ⁽¹⁾/2 x⁽¹⁾(i) = d⁽¹⁾(2i + 1) 3 1 x⁽⁰⁾(i) = d⁽¹⁾(3i)M_(symb) ^(layer) = M_(symb) ⁽¹⁾/3 x⁽¹⁾(i) = d⁽¹⁾(3i + 1) x⁽²⁾(i) =d⁽¹⁾(3i + 2) 4 1 x⁽⁰⁾(i) = d^((n))(4i) M_(symb) ^(layer) = x⁽¹⁾(i) =d^((n))(4i + 1) M_(symb) ^((n))/4, n = 1 or 2 x⁽²⁾(i) = d^((n))(4i + 2)x⁽³⁾(i) = d^((n))(4i + 3)

FIG. 25 shows layer mapping according to a 12th embodiment of thepresent invention. Only a single codeword is transmitted at a rank 3 orlower. A change in an aspect of mapping each codeword to layers atdifferent ranks is minimized. In transmission using active rankadaptation, disparity between the MCS used in transmission and the CQIreported by the UE depending on the rank change can be minimized. Thiscan be shown by Tables 27 and 28.

Table 27

TABLE 27 Number Number Codeword-to-layer mapping, of layers of codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽⁰⁾(i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾ 2 1 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) =M_(symb) ⁽⁰⁾/2 x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) 3 1 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/3 x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) x⁽²⁾(i) = d⁽⁰⁾(3i + 2)4 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb) ^(layer) = x⁽¹⁾(i) = d⁽⁰⁾(3i + 1)M_(symb) ⁽⁰⁾/3 = M_(symb) ⁽¹⁾ x⁽²⁾(i) = d⁽⁰⁾(3i + 2) x⁽³⁾(i) = d⁽¹⁾(i) 52 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) = x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) M_(symb)⁽⁰⁾/2 = M_(symb) ⁽¹⁾/3 x⁽²⁾(i) = d⁽¹⁾(3i) x⁽³⁾(i) = d⁽¹⁾(3i + 1) x⁽⁴⁾(i)= d⁽¹⁾(3i + 2) 6 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb) ^(layer) = x⁽¹⁾(i) =d⁽⁰⁾(3i + 1) M_(symb) ⁽⁰⁾/3 = M_(symb) ⁽¹⁾/3 x⁽²⁾(i) = d⁽⁰⁾(3i + 2)x⁽³⁾(i) = d⁽¹⁾(3i) x⁽⁴⁾(i) = d⁽¹⁾(3i + 1) x⁽⁵⁾(i) = d⁽¹⁾(3i + 2)

Table 28

TABLE 28 Number of Number of Codeword-to-layer mapping, layers codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 7 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/3 = x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) M_(symb) ⁽¹⁾/4x⁽²⁾(i) = d⁽⁰⁾(3i + 2) x⁽³⁾(i) = d⁽¹⁾(4i) x⁽⁴⁾(i) = d⁽¹⁾(4i + 1) x⁽⁵⁾(i)= d⁽¹⁾(4i + 2) x⁽⁶⁾(i) = d⁽¹⁾(4i + 3) 8 2 x⁽⁰⁾(i) = d⁽⁰⁾(4i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/4 = x⁽¹⁾(i) = d⁽⁰⁾(4i + 1) M_(symb) ⁽¹⁾/4x⁽²⁾(i) = d⁽⁰⁾(4i + 2) x⁽³⁾(i) = d⁽⁰⁾(4i + 3) x⁽⁴⁾(i) = d⁽¹⁾(4i) x⁽⁵⁾(i)= d⁽¹⁾(4i + 1) x⁽⁶⁾(i) = d⁽¹⁾(4i + 2) x⁽⁷⁾(i) = d⁽¹⁾(4i + 3)

FIG. 26 shows extended mapping in layer mapping according to the 12thembodiment of the present invention. The extended mapping is used tosupport HARQ retransmission or rank overriding, and this can be shown byTable 29.

Table 29

TABLE 29 Number of Number of Codeword-to-layer mapping, layers codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽¹⁾(i) M_(symb)^(layer) = M_(symb) ⁽¹⁾ 2 1 x⁽⁰⁾(i) = d⁽¹⁾(2i) M_(symb) ^(layer) =x⁽¹⁾(i) = d⁽¹⁾(2i + 1) M_(symb) ⁽¹⁾/2 3 1 x⁽⁰⁾(i) = d⁽¹⁾(3i) M_(symb)^(layer) = x⁽¹⁾(i) = d⁽¹⁾(3i + 1) M_(symb) ⁽¹⁾/3 x⁽²⁾(i) = d⁽¹⁾(3i + 2)4 1 x⁽⁰⁾(i) = d^((n))(4i) M_(symb) ^(layer) = x⁽¹⁾(i) = d^((n))(4i + 1)M_(symb) ^((n))/4, n = 1 or 2 x⁽²⁾(i) = d^((n))(4i + 2) x⁽³⁾(i) =d^((n))(4i + 3)

FIG. 27 shows layer mapping according to a 13th embodiment of thepresent invention. When the receiver performs the SIC, layer mapping oneach codeword is naturally increased according to a codeword index alongwith the increase of the ranks while codeword symbols mapped to eachlayer are equalized as mush as possible, thereby optimizing codeworddecoding performance. This can be shown by Tables 30 and 31.

Table 30

TABLE 30 Number of Number of Codeword-to-layer mapping, layers codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽⁰⁾(i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾ 2 2 x⁽⁰⁾(i) = d⁽⁰⁾(i) M_(symb) ^(layer) =M_(symb) ⁽⁰⁾ = x⁽¹⁾(i) = d⁽¹⁾(i) M_(symb) ⁽¹⁾ 3 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i)M_(symb) ^(layer) = M_(symb) ⁽⁰⁾/2 = x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) M_(symb) ⁽¹⁾x⁽²⁾(i) = d⁽¹⁾(i) 4 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) = M_(symb)⁽⁰⁾/2 = x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) M_(symb) ⁽¹⁾/2 x⁽²⁾(i) = d⁽¹⁾(2i) x⁽³⁾(i)= d⁽¹⁾(2i + 1) 5 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb) ^(layer) = M_(symb) ⁽⁰⁾/3= x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) M_(symb) ⁽¹⁾/2 x⁽²⁾(i) = d⁽⁰⁾(3i + 2) x⁽³⁾(i) =d⁽¹⁾(2i) x⁽⁴⁾(i) = d⁽¹⁾(2i + 1) 6 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb) ^(layer)= M_(symb) ⁽⁰⁾/3 = x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) M_(symb) ⁽¹⁾/3 x⁽²⁾(i) =d⁽⁰⁾(3i + 2) x⁽³⁾(i) = d⁽¹⁾(3i) x⁽⁴⁾(i) = d⁽¹⁾(3i + 1) x⁽⁵⁾(i) =d⁽¹⁾(3i + 2)

Table 31

TABLE 31 Number of Number of Codeword-to-layer mapping, layers codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 7 2 x⁽⁰⁾(i) = d⁽⁰⁾(4i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/4 = x⁽¹⁾(i) = d⁽⁰⁾(4i + 1) M_(symb) ⁽¹⁾/3x⁽²⁾(i) = d⁽⁰⁾(4i + 2) x⁽³⁾(i) = d⁽⁰⁾(4i + 3) x⁽⁴⁾(i) = d⁽¹⁾(3i) x⁽⁵⁾(i)= d⁽¹⁾(3i + 1) x⁽⁶⁾(i) = d⁽¹⁾(3i + 2) 8 2 x⁽⁰⁾(i) = d⁽⁰⁾(4i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/4 = x⁽¹⁾(i) = d⁽⁰⁾(4i + 1) M_(symb) ⁽¹⁾/4x⁽²⁾(i) = d⁽⁰⁾(4i + 2) x⁽³⁾(i) = d⁽⁰⁾(4i + 3) x⁽⁴⁾(i) = d⁽¹⁾(4i) x⁽⁵⁾(i)= d⁽¹⁾(4i + 1) x⁽⁶⁾(i) = d⁽¹⁾(4i + 2) x⁽⁷⁾(i) = d⁽¹⁾(4i + 3)

FIG. 28 shows extended mapping when layer mapping is performed accordingto the 13th embodiment of the present invention. The extended mapping isused to support HARQ retransmission or rank overriding, and this can beshown by Table 32.

Table 32

TABLE 32 Number of Number of Codeword-to-layer mapping, layers codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽¹⁾(i) M_(symb)^(layer) = M_(symb) ⁽¹⁾ 2 1 x⁽⁰⁾(i) = d^((n))(2i) M_(symb) ^(layer) =x⁽¹⁾(i) = d^((n))(2i + 1) M_(symb) ^((n))/2, n = 1 or 2 3 1 x⁽⁰⁾(i) =d^((n))(3i) M_(symb) ^(layer) = x⁽¹⁾(i) = d^((n))(3i + 1) M_(symb)^((n))/3, n = 1 or 2 x⁽²⁾(i) = d^((n))(3i + 2) 4 1 x⁽⁰⁾(i) = d^((n))(4i)M_(symb) ^(layer) = x⁽¹⁾(i) = d^((n))(4i + 1) M_(symb) ^((n))/4, n = 1or 2 x⁽²⁾(i) = d^((n))(4i + 2) x⁽³⁾(i) = d^((n))(4i + 3)

FIG. 29 shows layer mapping according to a 14th embodiment of thepresent invention. Only a single codeword is transmitted for a rank 2 orlower by basically using the layer mapping according to the 13thembodiment. Thus, when the SCI gain of the receiver is small,transmission performance can be improved by increasing a channel codinggain of the single codeword. This can be shown by Tables 33 and 34.

Table 33

TABLE 33 Number of Number of Codeword-to-layer mapping, layers codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽⁰⁾(i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾ 2 1 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) =M_(symb) ⁽⁰⁾/2 x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) 3 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/2 = x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) M_(symb) ⁽¹⁾ x⁽²⁾(i)= d⁽¹⁾(i) 4 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) = M_(symb) ⁽⁰⁾/2 =x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) M_(symb) ⁽¹⁾/2 x⁽²⁾(i) = d⁽¹⁾(2i) x⁽³⁾(i) =d⁽¹⁾(2i + 1) 5 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb) ^(layer) = M_(symb) ⁽⁰⁾/3 =x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) M_(symb) ⁽¹⁾/2 x⁽²⁾(i) = d⁽⁰⁾(3i + 2) x⁽³⁾(i) =d⁽¹⁾(2i) x⁽⁴⁾(i) = d⁽¹⁾(2i + 1) 6 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb) ^(layer)= M_(symb) ⁽⁰⁾/3 = x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) M_(symb) ⁽¹⁾/3 x⁽²⁾(i) =d⁽⁰⁾(3i + 2) x⁽³⁾(i) = d⁽¹⁾(3i) x⁽⁴⁾(i) = d⁽¹⁾(3i + 1) x⁽⁵⁾(i) =d⁽¹⁾(3i + 2)

Table 34

TABLE 34 Number of Number of Codeword-to-layer mapping, layers codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 7 2 x⁽⁰⁾(i) = d⁽⁰⁾(4i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/4 = x⁽¹⁾(i) = d⁽⁰⁾(4i + 1) M_(symb) ⁽¹⁾/3x⁽²⁾(i) = d⁽⁰⁾(4i + 2) x⁽³⁾(i) = d⁽⁰⁾(4i + 3) x⁽⁴⁾(i) = d⁽¹⁾(3i) x⁽⁵⁾(i)= d⁽¹⁾(3i + 1) x⁽⁶⁾(i) = d⁽¹⁾(3i + 2) 8 2 x⁽⁰⁾(i) = d⁽⁰⁾(4i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/4 = x⁽¹⁾(i) = d⁽⁰⁾(4i + 1) M_(symb) ⁽¹⁾/4x⁽²⁾(i) = d⁽⁰⁾(4i + 2) x⁽³⁾(i) = d⁽⁰⁾(4i + 3) x⁽⁴⁾(i) = d⁽¹⁾(4i) x⁽⁵⁾(i)= d⁽¹⁾(4i + 1) x⁽⁶⁾(i) = d⁽¹⁾(4i + 2) x⁽⁷⁾(i) = d⁽¹⁾(4i + 3)

FIG. 30 shows extended mapping when layer mapping is performed accordingto the 14th embodiment of the present invention. The extended mapping isused to support HARQ retransmission or rank overriding, and this can beshown by Table 35.

Table 35

TABLE 35 Number of Number of Codeword-to-layer mapping, layers codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽¹⁾(i) M_(symb)^(layer) = M_(symb) ⁽¹⁾ 2 1 x⁽⁰⁾(i) = d⁽¹⁾(2i) M_(symb) ^(layer) =x⁽¹⁾(i) = d⁽¹⁾(2i + 1) M_(symb) ⁽¹⁾/2 3 1 x⁽⁰⁾(i) = d^((n))(3i) M_(symb)^(layer) = x⁽¹⁾(i) = d^((n))(3i + 1) M_(symb) ^((n))/3, n = 1 or 2x⁽²⁾(i) = d^((n))(3i + 2) 4 1 x⁽⁰⁾(i) = d^((n))(4i) M_(symb) ^(layer) =x⁽¹⁾(i) = d^((n))(4i + 1) M_(symb) ^((n))/4, n = 1 or 2 x⁽²⁾(i) =d^((n))(4i + 2) x⁽³⁾(i) = d^((n))(4i + 3)

FIG. 31 shows layer mapping according to a 15th embodiment of thepresent invention. Only a single codeword is transmitted for a rank 3 orlower by basically using the layer mapping according to the 13thembodiment. Thus, when the SCI gain of the receiver is small,transmission performance can be improved by increasing a channel codinggain of the single codeword. This can be shown by Tables 36 and 37.

Table 36

TABLE 36 Number of Number of Codeword-to-layer mapping, layers codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽⁰⁾(i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾ 2 1 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) =M_(symb) ⁽⁰⁾/2 x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) 3 1 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/3 x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) x⁽²⁾(i) = d⁽⁰⁾(3i + 2)4 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) = M_(symb) ⁽⁰⁾/2 = x⁽¹⁾(i) =d⁽⁰⁾(2i + 1) M_(symb) ⁽¹⁾/2 x⁽²⁾(i) = d⁽¹⁾(2i) x⁽³⁾(i) = d⁽¹⁾(2i + 1) 52 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb) ^(layer) = M_(symb) ⁽⁰⁾/3 = x⁽¹⁾(i) =d⁽⁰⁾(3i + 1) M_(symb) ⁽¹⁾/2 x⁽²⁾(i) = d⁽⁰⁾(3i + 2) x⁽³⁾(i) = d⁽¹⁾(2i)x⁽⁴⁾(i) = d⁽¹⁾(2i + 1) 6 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb) ^(layer) =M_(symb) ⁽⁰⁾/3 = x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) M_(symb) ⁽¹⁾/3 x⁽²⁾(i) =d⁽⁰⁾(3i + 2) x⁽³⁾(i) = d⁽¹⁾(3i) x⁽⁴⁾(i) = d⁽¹⁾(3i + 1) x⁽⁵⁾(i) =d⁽¹⁾(3i + 2)

Table 37

TABLE 37 Number of Number of Codeword-to-layer mapping, layers codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 7 2 x⁽⁰⁾(i) = d⁽⁰⁾(4i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/4 = x⁽¹⁾(i) = d⁽⁰⁾(4i + 1) M_(symb) ⁽¹⁾/3x⁽²⁾(i) = d⁽⁰⁾(4i + 2) x⁽³⁾(i) = d⁽⁰⁾(4i + 3) x⁽⁴⁾(i) = d⁽¹⁾(3i) x⁽⁵⁾(i)= d⁽¹⁾(3i + 1) x⁽⁶⁾(i) = d⁽¹⁾(3i + 2) 8 2 x⁽⁰⁾(i) = d⁽⁰⁾(4i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/4 = x⁽¹⁾(i) = d⁽⁰⁾(4i + 1) M_(symb) ⁽¹⁾/4x⁽²⁾(i) = d⁽⁰⁾(4i + 2) x⁽³⁾(i) = d⁽⁰⁾(4i + 3) x⁽⁴⁾(i) = d⁽¹⁾(4i) x⁽⁵⁾(i)= d⁽¹⁾(4i + 1) x⁽⁶⁾(i) = d⁽¹⁾(4i + 2) x⁽⁷⁾(i) = d⁽¹⁾(4i + 3)

FIG. 32 shows extended mapping when layer mapping is performed accordingto the 15th embodiment of the present invention. The extended mapping isused to support HARQ retransmission or rank overriding, and this can beshown by Table 38.

Table 38

TABLE 38 Number of Number of Codeword-to-layer mapping, layers codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 2 1 x⁽⁰⁾(i) = d⁽¹⁾(2i) M_(symb)^(layer) = x⁽¹⁾(i) = d⁽¹⁾(2i + 1) M_(symb) ⁽¹⁾/2 3 1 x⁽⁰⁾(i) = d⁽¹⁾(3i)M_(symb) ^(layer) = x⁽¹⁾(i) = d⁽¹⁾(3i + 1) M_(symb) ⁽¹⁾/3 x⁽²⁾(i) =d⁽¹⁾(3i + 2) 4 1 x⁽⁰⁾(i) = d^((n))(4i) M_(symb) ^(layer) = x⁽¹⁾(i) =d^((n))(4i + 1) M_(symb) ^((n))/4, n = 1 or 2 x⁽²⁾(i) = d^((n))(4i + 2)x⁽³⁾(i) = d^((n))(4i + 3)

FIG. 33 shows layer mapping according to a 16th embodiment of thepresent invention. Only a single codeword is transmitted for a rank 3 orlower by basically using the layer mapping according to the 13thembodiment.

A change in an aspect of mapping each codeword to layers at differentranks is minimized. In transmission using active rank adaptation,disparity between the MCS used in transmission and the CQI reported bythe UE depending on the rank change can be minimized. This can be shownby Tables 39 and 40.

Table 39

TABLE 39 Number of Number of Codeword-to-layer mapping, layers codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽⁰⁾(i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾ 2 1 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer) =x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) M_(symb) ⁽⁰⁾/2 3 1 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb)^(layer) = x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) M_(symb) ⁽⁰⁾/3 x⁽²⁾(i) = d⁽⁰⁾(3i + 2)4 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb) ^(layer) = x⁽¹⁾(i) = d⁽⁰⁾(3i + 1)M_(symb) ⁽⁰⁾/3 = M_(symb) ⁽¹⁾ x⁽²⁾(i) = d⁽⁰⁾(3i + 2) x⁽³⁾(i) = d⁽¹⁾(i) 52 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb) ^(layer) = x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) M_(symb)⁽⁰⁾/3 = M_(symb) ⁽¹⁾/2 x⁽²⁾(i) = d⁽⁰⁾(3i + 2) x⁽³⁾(i) = d⁽¹⁾(2i) x⁽⁴⁾(i)= d⁽¹⁾(2i + 1) 6 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M_(symb) ^(layer) = M_(symb) ⁽⁰⁾/3= x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) M_(symb) ⁽¹⁾/3 x⁽²⁾(i) = d⁽⁰⁾(3i + 2) x⁽³⁾(i) =d⁽¹⁾(3i) x⁽⁴⁾(i) = d⁽¹⁾(3i + 1) x⁽⁵⁾(i) = d⁽¹⁾(3i + 2)

Table 40

TABLE 40 Number of Number of Codeword-to-layer mapping, layers codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 7 2 x⁽⁰⁾(i) = d⁽⁰⁾(4i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/4 = x⁽¹⁾(i) = d⁽⁰⁾(4i + 1) M_(symb) ⁽¹⁾/3x⁽²⁾(i) = d⁽⁰⁾(4i + 2) x⁽³⁾(i) = d⁽⁰⁾(4i + 3) x⁽⁴⁾(i) = d⁽¹⁾(3i) x⁽⁵⁾(i)= d⁽¹⁾(3i + 1) x⁽⁶⁾(i) = d⁽¹⁾(3i + 2) 8 2 x⁽⁰⁾(i) = d⁽⁰⁾(4i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/4 = x⁽¹⁾(i) = d⁽⁰⁾(4i + 1) M_(symb) ⁽¹⁾/4x⁽²⁾(i) = d⁽⁰⁾(4i + 2) x⁽³⁾(i) = d⁽⁰⁾(4i + 3) x⁽⁴⁾(i) = d⁽¹⁾(4i) x⁽⁵⁾(i)= d⁽¹⁾(4i + 1) x⁽⁶⁾(i) = d⁽¹⁾(4i + 2) x⁽⁷⁾(i) = d⁽¹⁾(4i + 3)

FIG. 34 shows extended mapping when layer mapping is performed accordingto the 16th embodiment of the present invention. The extended mapping isused to support HARQ retransmission or rank overriding, and this can beshown by Table 41.

Table 41

TABLE 41 Number Number of Codeword-to-layer mapping, of layers codewordsi = 0, 1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽¹⁾(i) M_(symb)^(layer) = M_(symb) ⁽¹⁾ 2 1 x⁽⁰⁾(i) = d⁽¹⁾(2i) M_(symb) ^(layer) =x⁽¹⁾(i) = d⁽¹⁾(2i + 1) M_(symb) ⁽¹⁾/2 3 1 x⁽⁰⁾(i) = d⁽¹⁾(3i) M_(symb)^(layer) = x⁽¹⁾(i) = d⁽¹⁾(3i + 1) M_(symb) ⁽¹⁾/3 x⁽²⁾(i) = d⁽¹⁾(3i + 2)4 1 x⁽⁰⁾(i) = d^((n))(4i) M_(symb) ^(layer) = x⁽¹⁾(i) = d^((n))(4i + 1)M_(symb) ^((n))/4, n = 1 or 2 x⁽²⁾(i) = d^((n))(4i + 2) x⁽³⁾(i) =d^((n))(4i + 3)

According to the aforementioned embodiments, layer mapping methods forall possible ranks with respect to 6 antenna ports and 8 antenna portsare introduced for exemplary purposes only. Various modifications can bemade therein by those skilled in the art by combining some or all of themapping methods described in these embodiments.

Extended mapping is a combination of available layers when the number ofavailable layers is decreased in basic layer mapping. If layer mappingwhich is a basis of the extended mapping is referred to as basicmapping, the number of available layers is decreased for the followingreasons. First, HARQ transmission is one of the reasons. Tt is assumedthat, in the basic mapping, the first codeword and the second codewordare initially transmitted, and transmission of the first codeword issuccessful whereas transmission of the second codeword fails. Since itis sufficient to retransmit the second codeword, the extended mapping isdefined for the retransmission of the second codeword. Second, rankoverriding or restriction is one of the reasons. Although the basismapping is used between the BS and the UE, if necessary, the BS may useonly some ranks or some parts of a precoding matrix index (PMI). As thenumber of layers is decreased, there is a need to define the extendedmapping.

FIG. 35 is a flow diagram showing triggering from basic mapping toextended mapping by HARQ retransmission. In step S810, a BS transmits afirst codeword CW1 and a second codeword CW2 to a UE by using basicmapping. For example, the basic mapping may be performed when a rank is2 in the embodiment of FIG. 3. The BS may report control information fordecoding of the first codeword CW1 and the second codeword CW2, e.g., anMCS index of the first codeword CW1 and an MCS index of the secondcodeword CW2, to the UE.

In step S820, since no error is detected from the first codeword CW1,and an error is detected from the second codeword CW2, thus the UEtransmits an acknowledgement (ACK) signal for the first codeword CW1,and transmits a negative-ACK (NACK) signal for the second codeword CW2.

Tn step S803, the BS retransmits the second codeword CW2 by using theextended mapping. For example, the extended mapping may be performedwhen a rank is 1 in the embodiment of FIG. 4 which is extended mappingfor layer mapping of the embodiment of FIG. 3. To indicate the extendedmapping, triggering to the extended mapping may be indicated by using atriggering indicator. Some parts of the re-transmitted controlinformation for decoding of the second codeword CW2 may be set to aspecific value. For example, when the MCS index is set to the specificvalue, the UE can confirm that the extended mapping is used intransmission.

Although downlink HARQ is exemplified, the present invention is notlimited thereto. Thus, the present invention may also apply to uplinkHARQ in which the UE transmits uplink data and in which the BS requestsretransmission.

FIG. 36 is a flowchart showing triggering from basic mapping to extendedmapping. In step S910, the basic mapping is established between a BS anda UE. The basic mapping is a basic layer mapping scheme for transmittingand/or receiving data between the BS and the UE. In step S920, the BSdetermines whether the extended mapping is used. The extended mappingmay be used when the UE is instructed to report a channel condition fora restricted rank. Alternatively, the extended mapping may be used forHARQ transmission. The extended mapping may also be used when layermapping is performed for downlink data in a state that the rank reportedby the UE is overridden. In step S930, the BS instructs the use ofextended mapping. The BS reports the use of extended mapping to the UEso that the UE is ready to perform an operation based on the extendedmapping.

FIG. 37 is a flowchart showing a method of data transmission accordingto an embodiment of the present invention. This method may be carried ina BS at downlink transmission or in a UE at uplink transmission.

In step S1010, the number of layers is determined. In step S1020,mapping symbols are generated by mapping modulation symbols for a firstcodeword and modulation symbols for a second codeword to each layer. Atleast one of the first codeword and the second codeword may be mapped to3 layers and the number of layers may be larger than 3. Layer mappingschemes shown in FIGS. 3-34 may be used. In step S1030, the mappingsymbols are transmitted through a plurality of antennas.

The number of layers may be changed in order to perform HARQ or rankoverriding. In step S1040, the number of layers is changed. The numberof layers after changed may be smaller than the number of layers beforechanged. In step S1050, new mapping symbols is generated by mapping themodulation symbols for the first codeword or the mapping modulationsymbols for the second codeword to each layer. Layer mapping schemesshown in FIGS. 3-34 may be used. In step S1060, the new mapping symbolsare transmitted through the plurality of antennas.

FIG. 38 is a block diagram showing a transmitter according to anembodiment of the present invention. A transmitter 900 includes aprocessor 910 and a radio frequency (RF) unit 920. The processor 910 mayimplements at least one embodiment among embodiments shown in FIGS.3-37. The RF unit 920 is connected to the processor 910 to transmitand/or receive radio signals through multiple Tx antennas. In uplink,the transmitter 900 may be a part of a UE. In downlink, the transmitter900 may be a part of a BS.

FIG. 39 is a flowchart showing a method of communication according to anembodiment of the present invention. This method may be carried in a UEat downlink transmission or in a BS at uplink transmission.

In step S1110, the number of layers is acquired. The number of layersmay be larger than 3. The number of layers may be received throughsystem information, a RRC message or resource assignment.

In step S1120, mapping symbols are received. The mapping symbols may bemapped to each layer according to one layer mapping schemes shown inFIGS. 3-34.

In step S1130, the mapping symbols are demapped to generate modulationsymbols for a first codeword or modulation symbols for a secondcodeword. At least one of the first codeword and the second codeword maybe mapped to at least 3 layers.

After demapping, the first codeword may be reproduced from themodulation symbols for the first codeword. The second codeword may bereproduced from the modulation symbols for the second codeword. Thereproducing the codword from modulation symbols may be achieved byperforming demodulation and decoding well known in the skilled art.

It can be understood that skilled in the art may reproduce a codewordfrom mapping symbols by reversely performing procedure shown inembodiments of FIG. 37 or apparatus of FIG. 2.

The layer mapping methods or other methods described in theaforementioned embodiments can be performed only at some ranks. Forexample, ranks 1, 2, 4, and 6 may be used in a system having 6 antennaports, and ranks 1, 2, 4, 6, and 8 may be used in a system having 8antenna ports. That is, instead of using all possible ranks, only someranks may be used by considering a signal overhead, system complexity,and difference in performance of each rank. An available rank may bepredetermined, or may be reported by the BS to the UE through upperlayer signaling or L1/L2 signaling.

In case of upper layer signaling, an RRC parameter of “Codebook subsetrestriction indicator” with an extended bit-width (i.e., bit-map size)may be used to indicate the situation of restricted rank utilization. Incase of predetermination, an RRC parameter of“codebookSubsetRestriction” may have the bit-width in which the statesof this RRC parameter express the additional restriction of PMI usagefor given available rank cases.

The layer mapping methods or other methods described in theaforementioned embodiments may be used by combining some ranks. Forexample, ranks 1 to 3 may be selected in the layer mapping method of the1st embodiment and ranks 4 to 6 may be selected in the layer mappingmethod of the 2nd embodiment, so that a layer mapping method obtained bycombining the two methods is used in a system having 6 antenna ports.For another example, among mapping methods of the respectiveembodiments, at least one mapping method corresponding to each rank maybe selected to configure a new mapping method by combining the selectedmapping methods. In addition, among extended mapping methods of therespective embodiments, at least one extended mapping methodcorresponding to each rank may be selected to configure a new extendedmapping method by combining the selected extended mapping methods.

In the aforementioned embodiments, M^((q)) _(symb) may denote a totalnumber of modulation symbols for a codeword q, or may denote the numberof some modulation symbols constituting the codeword q. That is, ifM^((q),tot) _(symb) denotes a total number of modulation symbols for thecodeword q, the following relation may be satisfied: 1<M^((q))_(symb)≦M^((q),tot) _(symb). If M^((q)) _(symb)=M^((q),tot) _(symb), thebasic layer mapping may be M^((q)) _(symb)<M^((q),tot) _(symb) in caseof extended mapping for the basic layer mapping. M^((q)) _(symb) in usemay differ for each rank.

In the aforementioned embodiments, it is introduced that layers mappedto each codeword are sequentially mapped in an index order. However,indices of the layers may vary according to time or other situations.The indices of the layers may vary by a predetermined offset or in anarbitrary manner. Alternatively, the indices of the layers may vary byan offset predetermined according to a specific period or may vary in anarbitrary manner.

The layer mapping and/or extended mapping methods of each embodiment maybe combined in a cell unit and/or a time unit. For example, the layermapping of the 1st embodiment is used for all or some ranks at a firsttime slot, and the layer mapping of the 2nd embodiment may be used forall or some ranks at a second time slot.

The present invention can be implemented with hardware, software, orcombination thereof. In hardware implementation, the present inventioncan be implemented with one of an application specific integratedcircuit (ASIC), a digital signal processor (DSP), a programmable logicdevice (PLD), a field programmable gate array (FPGA), a processor, acontroller, a microprocessor, other electronic units, and combinationthereof, which are designed to perform the aforementioned functions. Insoftware implementation, the present invention can be implemented with amodule for performing the aforementioned functions. Software is storablein a memory unit and executed by the processor. Various means widelyknown to those skilled in the art can be used as the memory unit or theprocessor.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those skilled in the art that various changes in form and details maybe made therein without departing from the spirit and scope of theinvention as defined by the appended claims. The exemplary embodimentsshould be considered in descriptive sense only and not for purposes oflimitation. Therefore, the scope of the invention is defined not by thedetailed description of the invention but by the appended claims, andall differences within the scope will be construed as being included inthe present invention.

1-10. (canceled)
 11. A transmitter, the transmitter comprising: a radiofrequency (RF) unit for transmitting and receiving a radio signal; and aprocessor coupled to the RF unit, wherein the processor is configuredfor: generating mapping symbols by mapping modulation symbols for afirst codeword and modulation symbols for a second codeword to aplurality of layers; and transmitting the mapping symbols through aplurality of antennas, wherein when a number of the plurality of layersis larger than 4, at least one of the modulation symbols for firstcodeword and the modulation symbols for the second codeword is mapped toat least 3 layers and, wherein when the number of the plurality oflayers is 5, the modulation symbols for for the first codeword aremapped to 2 layers and the modulation symbols for the second codewordare mapped to remaining 3 layers, and when the number of the pluralityof layers is 6, the modulation symbols for for the first codeword aremapped to 3 layers and the modulation symbols for the second codewordare mapped to remaining 3 layers, and when the number of the pluralityof layers is 7, the modulation symbols for for the first codeword aremapped to 3 layers and the modulation symbols for the second codewordare mapped to remaining 4 layers, and when the number of the pluralityof layers is 8, the modulation symbols for for the first codeword aremapped to 4 layers and the modulation symbols for the second codewordare mapped to remaining 4 layers.
 12. The transmitter of claim 11,wherein the number of the plurality of antennas is larger than 3 and thenumber of the plurality of layers is smaller than or equal to a numberof the plurality of antennas.
 13. The transmitter of claim 11, theprocessor is further configured for: determining the number of theplurality of layers.
 14. The transmitter of claim 11, wherein when thenumber of the plurality of layers is 5, 6, 7 or 8, the modulationsymbols for the first codeword and the modulation symbols for the secondcodeword are mapped to layers according to below table. Number of theCodeword-to-layer mapping plurality i = 0, 1, . . . , M^(layer)_(symb − 1,) of Number of M^(layer) _(symb): a number of modulationsymbols for each layers codewords layer of the plurality of layers 5 2x⁽⁰⁾(i) = d⁽⁰⁾(2i) M^(layer) _(symb) = M^((o)) _(symb)/2 = x⁽¹⁾(i) =d⁽⁰⁾(2i + 1) M⁽¹⁾ _(symb)/3 x⁽²⁾(i) = d⁽¹⁾(3i) x⁽³⁾(i) = d⁽¹⁾(3i + 1)x⁽⁴⁾(i) = d⁽¹⁾(3i + 2) 6 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M^(layer) _(symb) =M^((o)) _(symb)/3 = x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) M⁽¹⁾ _(symb)/3 x⁽²⁾(i) =d⁽⁰⁾(3i + 2) x⁽³⁾(i) = d⁽¹⁾(3i) x⁽⁴⁾(i) = d⁽¹⁾(3i + 1) x⁽⁵⁾(i) =d⁽¹⁾(3i + 2) 7 2 x⁽⁰⁾(i) = d⁽⁰⁾(3i) M^(layer) _(symb) = M^((o))_(symb)/3 = x⁽¹⁾(i) = d⁽⁰⁾(3i + 1) M⁽¹⁾ _(symb)/4 x⁽²⁾(i) = d⁽⁰⁾(3i + 2)x⁽³⁾(i) = d⁽¹⁾(4i) x⁽⁴⁾(i) = d⁽¹⁾(4i + 1) x⁽⁵⁾(i) = d⁽¹⁾(4i + 2) x⁽⁶⁾(i)= d⁽¹⁾(4i + 3) 8 2 x⁽⁰⁾(i) = d⁽⁰⁾(4i) M^(layer) _(symb) = M^((o))_(symb)/4 = x⁽¹⁾(i) = d⁽⁰⁾(4i + 1) M⁽¹⁾ _(symb)/4 x⁽²⁾(i) = d⁽⁰⁾(4i + 2)x⁽³⁾(i) = d⁽⁰⁾(4i + 3) x⁽⁴⁾(i) = d⁽¹⁾(4i) x⁽⁵⁾(i) = d⁽¹⁾(4i + 1) x⁽⁶⁾(i)= d⁽¹⁾(4i + 2) x⁽⁷⁾(i) = d⁽¹⁾(4i + 3)

In the above table, d⁽⁰⁾(i) is the modulation symbols for the firstcodeword, d⁽¹⁾(i) is the modulation symbols for the second codeword,x^((n))(i) is mapping symbols mapped to layer n, M⁽⁰⁾ _(symb) is anumber of modulation symbols for the first codeword and M⁽¹⁾)_(symb) isa number of modulation symbols for the second codeword.
 15. A receiver,the receiver comprising: a radio frequency (RF) unit for transmittingand receiving a radio signal; and a processor coupled to the RF unit,wherein the processor is configured for: receiving mapping symbols whichare mapped to a plurality of layers; and demapping the mapping symbolsto generate modulation symbols for a first codeword and modulationsymbols for a second codeword, wherein when a number of the plurality oflayers is larger than 4, at least one of the modulation symbols for thefirst codeword and the modulation symbols for the second codeword ismapped to at least 3 layers, and wherein when the number of theplurality of layers is 5, the modulation symbols for for the firstcodeword are mapped to 2 layers and the modulation symbols for thesecond codeword are mapped to remaining 3 layers, and when the number ofthe plurality of layers is 6, the modulation symbols for for the firstcodeword are mapped to 3 layers and the modulation symbols for thesecond codeword are mapped to remaining 3 layers, and when the number ofthe plurality of layers is 7, the modulation symbols for for the firstcodeword are mapped to 3 layers and the modulation symbols for thesecond codeword are mapped to remaining 4 layers, and when the number ofthe plurality of layers is 8, the modulation symbols for for the firstcodeword are mapped to 4 layers and the modulation symbols for thesecond codeword are mapped to remaining 4 layers.